1. Field of the Invention
The invention relates to a displacement machine for compressible media, with at least four feed spaces arranged in a stationary housing, where, in the case of four feed spaces, each housing half has two feed spaces offset approximately 180.degree. relative to one another and extending spirally from an inlet to an outlet, and there is assigned to each feed space a displacement body engaging in this and held vertically, as a spiral strip, on a disk-shaped rotor which can be driven eccentrically relative to the housing and for the guidance of which in the housing there is a second guide eccentric arrangement arranged at a distance from the first drive eccentric arrangement.
2. Discussion of Background
Displacement machines of the type mentioned are known, for example, from No. DE-C3-2,603,462. These machines are characterized by a virtually pulsation-free conveyance of the gaseous working medium consisting, for example, of air or an air/fuel mixture and can therefore also be used advantageously for the purposes of the super-charging of internal-combustion engines. During the operation of such a displacement machine working as a compressor, several approximately sickle-shaped working spaces are enclosed along the feed chamber between the spiral displacement body and the two cylinder walls of the feed chamber, as a result of a differing curvature of the spiral forms, and move through the feed chamber from a working-medium inlet towards a working-medium outlet, their volume being constantly reduced and the pressure of the working medium being increased correspondingly. The displacement bodies are formed by spiral strips which are held essentially vertically on the disk-shaped rotor and which have a relatively large axial length in comparison with their thickness. Similar conditions prevail on the side of the stationary housing, where spiral strip-like webs of relatively great length in the axial and peripheral directions in relation to the wall thickness likewise stand between the feed chambers.
Accurate rolling of a displacement body on the spiral principle as a result of a circular translational movement can be obtained by means of a double-crank mechanism, as is known, for example, from No. DE-A-3,107,231 and in which one crank drives and the second crank guides.
A serious problem arises when the displacement body having a large axial width is guided parallel to the housing inaccurately because of production deviations. No. DE-A-3,231,756 proposed to remedy this by making the guide element consist not of a crank, but of a crank rocker which is articulated on the housing at one end and on the displacement body at the other end and the length of which is greater than the length of the drive crank. Here too, the spiral strips are arranged so as to project axially on a disk having a hub for mounting the eccentric crank mechanism. The disk is radially flush with the strip, and the variable gap between the housing and the displacement body, caused as a result of movement, is then reduced to a minimum, without contact, by a special design of the guide element. At the same time, the longitudinal gaps are limited by overlapping radius-shaped surfaces of the housing, guide element and displacement body. An advantage of this type of guide and method of sealing is to be seen in the fact that the diameter of the disk-shaped rotor and consequently also of the housing can be reduced by the amount of double the crank length.
This advantage is not afforded in a design according to No. DE-A-3,107,231 which was mentioned in the introduction and which is used as a basis here. There, the rotor disk projects radially beyond the strip by an amount which, in any position of the displacement body, overlaps the housing recess then required. Sealing is then obtained by means of the axial gaps reduced to a minimum between the disk and the housing. However, this necessitates, on the one hand, a considerable increase in the size of the displacement body and housing and, on the other hand, a considerable increase in the number of sealing strips necessary.